The Devil We Know is a 2018 investigative documentary film by director Stephanie Soechtig regarding allegations of health hazards from perfluorooctanoic acid (PFOA, also known as C8), a key ingredient used in manufacturing Teflon, and DuPont's potential responsibility. PFAS are commonly found in every household, and in products as diverse as non-stick cookware, stain resistant furniture and carpets, wrinkle free and water repellant clothing, cosmetics, lubricants, paint, pizza boxes, popcorn bags, and many other everyday products.

Two of the most common types (PFOS and PFOA) were phased out of production in the United States (US) in 2002 and 2015 respectively, but are still present in some imported products, and were replaced by the similarly toxic GenX in Teflon products. PFOA and PFOS are found in every American person’s blood stream in the parts per billion range, though those concentrations have decreased by 70% for PFOA and 84% for PFOS between 1999 and 2014, which coincides with the end of the production and phase out of PFOA and PFOS in the US.

The film premiered at the 2018 Sundance Film Festival. The director, Soechtig, has also produced similar documentary exposés including Tapped (2009), about the pollution caused by bottled water, Fed Up (2014), dealing with the obesity-promoting food industry, and Under the Gun (2016), about the gun lobby. The documentary was also shown on BBC Four in November 2018 as Poisoning America – The Devil We Know as part of the BBC Storyville documentary series.